4-Halo-5-formyl thiazoles

ABSTRACT

The present invention relates to compounds obtained by condensing a compound of formula I,    &lt;IMAGE&gt;  I   or a salt thereof,  in which R is a primary, secondary or tertiary amino group, with a Vilsmeier reagent, and derivatives of such aldehydes.

The present application is a continuation-in-part of application Ser. No. 144,383, filed Apr. 28, 1980 and now abandoned.

The present invention relates to thiazole compounds and the process for their production.

It has been found that novel 4-halo-5-formyl-thiazoles are formed by condensing 4-oxy-thiazoles with a Vilsmeier reagent, for example, one based on phosphorousoxychloride and an amide.

More particularly, the present invention provides compounds obtained by condensing a compound of formula I, ##STR2## or a salt thereof, in which R is a primary, secondary or tertiary amino group,

with a Vilsmeier reagent,

and derivatives of such aldehydes.

The preferred Vilsmeier reagent is that from phosphorousoxychloride and dimethylformamide.

Preferred compounds according to the present invention are those of formula II, ##STR3## in which R₁ is --CHO, --CH═CR₄ R₅, --CN, --CH═NOH, --CH₂ OR₆, --CH═N-NHR₇, ##STR4## --CH(OH)CN or an open chain or cyclic acetal or thioacetal group, R' is a primary, secondary or tertiary amino or an imino group, with the provisos that R' is primary amino when R₁ is other than --CHO or --CH═CR₄ R₅ and R' is a secondary or tertiary amino group when R₁ is --CH═CR₄ R₅,

either, R₄ is hydrogen, cyano, alkylcarbonyl, benzoyl, alkylsulphonyl, phenylsulphonyl, alkylaminocarbonyl, dialkylaminocarbonyl, phenylaminocarbonyl, N-alkyl-N-phenylaminocarbonyl, aminocarbonyl, aminocarbonylaminocarbonyl, piperidinylcarbonyl, aminothiocarbonyl, benzimidazolyl-2 or --COOB, in which B is hydrogen; C₁₋₁₀ alkyl; C₅₋₇ cycloalkyl; C₁₋₆ alkyl substituted by up to three substituents selected from the group consisting of chlorine and bromine; C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxyl, cyano, phenoxy, alkoxy, carboxy, alkoxycarbonyl, alkylcarbonyloxy, alkoxycarbonyloxy, alkylaminocarbonyloxy, aminocarbonyl, alkylaminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, and phenyl, in which the phenyl ring is optionally substituted by 1 or 2 substituents selected from chlorine bromine and nitro, with the proviso that when such alkyl is substituted by a group containing a benzene ring it is monosubstituted and any substituted alkyl is free from acetal groups; or B is C₃₋₆ alkenyl optionally substituted by chlorine or bromine; or is alkynyl.

and R₅ is hydrogen, cyano, alkoxycarbonyl, nitro or 3-di-cyanomethylene-5-5-dimethylcyclohexen-1-yl with the proviso that when R₅ is the latter R₄ is hydrogen and when R₅ is nitro R₄ is hydrogen, methyl or ethyl,

or R₄ and R₅ together form a 5- or 6-membered carbocyclic or heterocyclic ring system,

R₆ is hydrogen, alkyl, alkylcarbonyl or benzyl in which the benzene ring is optionally substituted by up to two substituents selected from chlorine, bromine and nitro,

R₇ is hydrogen, alkyl, aminocarbonyl, amino thiocarbonyl or phenyl which is optionally substituted by 1 or 2 substituents selected from the group consisting of chlorine, bromine and nitro,

R₈ is hydrogen, chlorine, bromine, methyl, C₁₋₂ alkoxy, carboxyl, alkoxycarbonyl,

cyano or nitro, p1 m is 0 or 1,

and any alkyl and alkoxy groups or moieties in such compounds contain 1 to 4 carbon atoms and any alkenyl or alkynyl groups or moieties 3 to 4 carbon atoms, except when otherwise stated.

Preferred groups R', are those of formula

    --NR.sub.2 R.sub.3

in which either

R₂ is hydrogen; C₁₋₁₀ alkyl; C₂₋₃ alkyl substituted by hydroxy, cyano, chlorine, bromine, alkyl-C₁₋₂ carbonyl, alkoxy-C₁₋₄ carbonyloxy, alkylC₁₋₄ carbonyloxy, alkylamiocarbonyloxy, dialkylaminocarbonyloxy, alkoxyC₁₋₄ carbonyl,phenylaminocarbonyloxy or N-alkyl-N-phenylaminocarbonyloxy with the proviso that such substituted alkyl radicals are free from acetal groups; phenyl optionally substituted by 1 or 2 substituents selected from chlorine, bromine, methyl and nitro; alkenyl; dicyanoalkenyl; cyclohexyl; or naphthyl,

and R₃ has one of the significances of R₂ with the provisos that when one of R₂ and R₃ is naphthyl the other has a significance other than naphthyl or phenyl, and when one of R₂ and R₃ is dicyanoalkenyl the other is hydrogen,

or, R₂ and R₃ together with the nitrogen atom form a 5- or 6-membered heterocyclic ring, in particular piperidine, piperazine or morpholine,

or R₂ and R₃ together form a group of formula

    ═CH--(CH═CH).sub.m' NR.sub.10 R.sub.11

in which either,

R₁₀ is hydrogen or alkyl, and

R₁₁ is hydrogen, alkyl or phenyl,

or, R₁₀ and R₁₁ together with the N-atom form piperidine,

m' is 0 or 1, and

any alkyl groups and moieties contain 1 to 4 carbon atoms and any alkenyl group 3 to 4 carbon atoms except where otherwise stated.

When R₄ and R₅ together form a carbocyclic or heterocyclic ring system, preferred rings are ##STR5##

The preferred C₁₋₄ alkyl groups or moieties in significances for R₄ are those which contain 1 or 2 carbon atoms. The preferred alkenyl and alkynyl moieties are those which contain 3 or 4 carbon atoms.

R₂ is preferably R₂ ', where R₂ ' is hydrogen, C₁₋₄ alkyl, hydroxyethyl, cyanoethyl or phenyl and R₃ is preferably R₃ ', where R₃ ' is hydrogen, C₁₋₄ alkyl, allyl, cyclohexyl, or naphthyl, or R₂ ' and R₃ ' form a group of formula ═CH(CH═CH)_(m') NR₁₀ R₁₁, where R₁₀ and R₁₁ are C₁₋₄ alkyl, especially methyl, preferably with m'=O. Preferably when R₃ ' is cyclohexyl or phenyl R₂ ' is other than phenyl and when R₃ ' is naphthyl R₂ ' is preferably hydrogen.

R₁ is preferably R₁ ', where R₁ ' is --CHO, --CH═CR₄ R₅, --CH═NOH or CN, especially --CHO, --CH═CR₄ 'R₅ ', CN or --CH═NOH.

R₄ is preferably R₄ ', where R₄ ' is cyano; benzoyl; methylsulphonyl; phenylsulphonyl; methyl or ethylaminocarbonyl; phenylaminocarbonyl; aminocarbonyl; aminocarbonylaminocarbonyl; piperidinylcarbonyl; benzimidazolyl-2 or --COOB', where B' is C₁₋₁₀ alkyl, cyclohexyl, C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxy, cyano, C₁₋₂ alkoxy, carboxy, alkoxy(C₁₋₂)carbonyl, alkyl(C₁₋₂)carbonyloxy, C₁₋₂ alkoxycarbonyloxy, C₁₋₂ alkylaminocarbonyloxy, aminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, phenyl, chlorophenyl, nitrophenyl, with the proviso that when such alkyl is substituted by a group containing a benzene ring it is monosubstituted and any substituted alkyl is free from acetal groups; or B' is alkenyl optionally substituted by chlorine or bromine or is alkynyl.

R₅ is preferably R₅ ', where R₅ ' cyano, nitro or 3-dicyanomethylene-5,5-dimethylcyclohexen-1-yl with the proviso that when R₅ ' is any one of the latter two significances R₄ is hydrogen.

More preferably R₁ is R₁ ", where R₁ " is --CHO, or --CH═CR₄ R₅ especially --CHO or CH═CR₄ 'R₅ '. Most preferably R₁ is R₁ "', where R₁ "' is --CHO or --CH═C(CN)R₄ " where R₄ " is cyano, alkoxy(C₁₋₆)carbonyl, benzoyl, cyclohexyloxycarbonyl, C₃₋₄ -alkenyloxycarbonyl, chloro- or bromo-C₃₋₄ alkenyloxycarbonyl or alkoxy(C₁₋₆)carbonyl in which the alkyl group is substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxyl, phenyl, carboxy, alkoxyC₁₋₂ carbonyl, alkyl(C₁₋₂)carbonyloxy, C₁₋₂ alkylaminocarbonyloxy, alkoxyC₁₋₂ carbonyloxy, with --CHO being most preferred for R₁.

Preferred compounds of formula II are those in which R₁ is R₁ ', R₂ is R₂ ', R₃ is R₃ ' especially those where R₄ and R₅ are R₄ ' and R₅ '.

More preferred compounds of formula II are those in which R₁ is R₁ ", R₂ is R₂ ', R₃ is R₃ ' especially those where R₅ is cyano and R₄ is R₄ ".

Most preferred compounds of formula II are those in which R₁ is R₁ "', R₂ is R₂ ' and R₃ is R₃ ', especially those where m is 0.

The reaction of the compounds of formula I with a Vilsmeier reagent may be carried out in accordance with known methods. In general at least 2 mols, and when R is a primary amino group, preferably at least three mols Vilsmeier reagent are employed. When a primary amine of formula I is employed, the ═CH(CH═CH)_(m') NR₁₀ R₁₁ group attached to the 2-position can be hydrolytically split off, e.g. by heating the acid solution, when compounds of formula II wherein R₂ and R₃ are both hydrogen are desired.

Suitable amides for the Vilsmeier reagent include formamide, dimethylformamide, N-methylformanilide, formylpiperidine and vinyl-group-containing formyl compounds, for example (CH₃)₂ N--CH═CH--CHO, with dimethylformamide being especially preferred. The preferred acid halides for the Vilsmeier reagent are the acid chlorides, especially phosphorousoxychloride. When a vinyl-group containing Vilsmeier agent is employed compounds of formula II in which m and m' are 1 are obtained.

The formyl group in the compounds of formula II may be converted to any of the other significances for R₁ by known methods, for example condensation with a hydroxylamine and optionally with acylation to obtain compounds where R₁ is cyano; reaction with hydrazine or a derivative thereof; preparation of a cyanohydrin; preparation of Schiff bases, Knoevenagel, reduction to form an alcohol optionally with esterification or etherification etc.

It will be appreciated that hydrogen atoms on the amino group in the 2-position may be replaced by a protecting group before reacting the formyl compounds further and said protecting group can be subsequently split off.

The compounds of formula I are known or may be prepared by known methods from available starting materials.

The novel compounds according to the invention are useful as dyestuffs and/or as intermediates for the preparation of dyestuffs. Compounds which have a secondary or tertiary amino group in the 2-position and a formyl group in the 5-position can be reacted with compounds having an activated methylene group, for example malonic acid derivatives in accordance with the Knoevenagel reaction to obtain a compound of formula VI ##STR6## in which R₂ to R₅ are as defined above and at least one of R₂ and R₃ is other than hydrogen,

which compounds of formula VI are useful as disperse dyestuffs for dyeing or printing hydrophobic, high-molecular weight, synthetic or semi-synthetic organic substrates, for example cellulose 21/2 acetate, cellulose triacetate, polyesters and synthetic polyamides. The dyeings obtained have good fastness, and the dyestuffs have notable buildup power on polyester and give intense dyeings.

Compounds having a primary amino group in the 2-position are useful as dyestuff diazo components.

The following Examples further serve to illustrate the invention. In the Examples all parts and percentages are by weight and the temperatures are in degrees Centigrade.

EXAMPLE 1

46 Parts phosphorousoxychloride are added at 0° to 5° to 73 parts N,N-dimethylformamide. 15.2 Parts 2-aminothiazoline-4-one-hydrochloride are added portionwise at 0° to 5° to the colourless solution. The cooling bath is removed and the mixture is heated to 70°. After 14 hours stirring the mixture is allowed to cool and is poured carefully onto a mixture of 82 parts sodium acetate, 120 parts water and 100 parts ice. The brownish-red solution is neutralized by dropwise addition of approximately 120 parts 30% aqueous sodium hydroxide. The product 2-(dimethylaminomethinimino)-4-chloro-5-formyl-thiazole can be separated by filtration. Alternatively, the product without isolation, can be reacted with 1 part piperidine and 6.6 parts malonic acid dinitrile in 20 parts ethanol. After stirring for about 3 hours at room temperature condensation is complete. The product of formula ##STR7## which is filtered off and washed, dyes polyester fibres in yellow fluorescent shades.

EXAMPLE 2

The mixture containing 2-(dimethylaminomethinimino)-4-chloro-5-formyl-thiazole prepared as described in Example 1 (without having been neutralized) is stirred for 2 hours at 50° whereby the compound of formula ##STR8## crystallizes out. The yellow product is filtered off after the suspension has cooled. The product can be used without further purification to prepare azo dyestuffs by diazotization and coupling with a coupling component.

EXAMPLE 3

Preparation of the compound of formula ##STR9##

The aqueous suspension of 2-amino-4-chloro-5-formylthiazole prepared as described in Example 2 is adjusted to pH 5 with approximately 120 parts 30% aqueous sodium hydroxide, then 1 part piperidine and 6.6 parts malonic acid dinitrile in 20 parts ethanol are added thereto. Stirring is effected for 1 hour at room temperature and then 3 hours at 50°. The brown suspension is allowed to cool and the product is filtered off.

The product can also be produced in the following manner:

26.5 Parts of 2-(N,N'-dimethylaminomethinimino)-4-chloro-5-(2',2'-dicyanovinyl)-thiazole produced as described in Example 1 are suspended in 100 parts 50% sulphuric acid and stirred for approximately 18 hours at 50°. The mixture is left to cool and the product is filtered off.

Further compounds of formula II in which R is NR₂ R₃ and m is 0, which can be produced in analogy with the procedures of Examples 1 to 3, are given in the following Table.

                                      TABLE 1                                      __________________________________________________________________________     EX.                                                                            No.                                                                               R.sub.1                   R.sub.2  R.sub.3                                  __________________________________________________________________________     4  CHNOH                     H        H                                        5  CHNOH                     CHN(CH.sub.3).sub.2                               6  CHNNHC.sub.6 H.sub.5      H        H                                        7  CHO                       C.sub.6 H.sub.4 m-(CH.sub.                                                              C.sub.2 H.sub.5                          8  "                         C.sub.6 H.sub.33,4-Cl.sub.2                                                             CH.sub.3                                 9  "                         H        C.sub.6 H.sub.5                          10 "                         H        2-naphthyl                               11 CN                        H        H                                        12 CHO                       H                                                 Cyclohexyl                                                                     13 CHO                       C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                          14 CHO                       CH.sub.3 CH.sub.3                                 15 CHO                       CH.sub.3 C.sub.6 H.sub.5                          16                                                                                 ##STR10##                H        H                                          17                                                                              CH.sub.2 OH               H        H                                        18 CH.sub.2 OCOCH.sub.3      H        H                                        19 CH.sub.2OCH.sub.2 C.sub.6 H.sub.5 NO.sub.2 (p)                                                           H        CH.sub.2 C.sub.6 H.sub.44NO.sub. 2       20 CHO                       H        CH.sub.2 CHCH.sub.2                      21                                                                                 ##STR11##                CN(CH.sub.3)C.sub.6 H.sub.5                         22                                                                              CHC(CN)CONH.sub.2                                                                                         ##STR12##                                          23                                                                              CHC(CN)CONHCONH.sub.2     CHNH.sub.2                                        24 CN                        H        C.sub.6 H.sub.5                          25 CN                        H        1-Naphthyl                               26 CHO                       H        C.sub.2 H.sub.5                          27 CHO                       CHN(CH.sub.3)C.sub.6 H.sub.5                        28                                                                              CHO                                                                                                       ##STR13##                                          29                                                                              HCHCCHO                   CHCHCHN(CH.sub.3).sub.2                           30 HCHCNO.sub.2              H        H                                        31 HCCHCN                    H        H                                        32 HCCHCOOH                  H        H                                        33 HCCHCOOC.sub.2 H.sub.5    H        H                                        34 HCCHCOCH.sub.3            H        H                                        35 CHNC.sub. 6 H.sub.4(p)-NO.sub.2                                                                          H        H                                        36 CHNC.sub.6 H.sub.5        CHN(CH.sub.3).sub.2                                 37                                                                               ##STR14##                H        CH.sub.3                                   38                                                                              CHC(CN)COOCH.sub.2 C.sub.6 H.sub.5                                                                       H        H                                        39 CHC(CN)SO.sub.2C.sub.6 H.sub.5                                                                           H        H                                        40 CHC(CN)COOC.sub.2 H.sub.4 CN                                                                             H        H                                        41 CHC(CN)COOCH.sub.2 COOC.sub.2 H.sub.5                                                                    H        H                                        42 CNNHC.sub.6 H.sub.32,4-(NO.sub.2).sub.2                                                                  H        H                                        43 CHC(CN)COOCH.sub.3        H        H                                        44 CHC(CN)COOC.sub.2 H.sub.5 H        H                                        45 CHC(CN).sub.2             (CH.sub.2).sub.5                                  46 "                         (CH.sub.2).sub.2NCH.sub.3(CH.sub.2).sub.2         47 "                         (CH.sub.2).sub.2O(CH.sub.2).sub.2                 48 "                         H        C.sub.6 H.sub.32,4-(NO.sub.2).sub.2                                            1                                        49 CH(OH)CN                  H        H                                        50 CHO                       CH.sub.2 CH.sub.2 OH                                                                    C.sub.6 H.sub.5                          51 CHO                       H        n-C.sub.4 H.sub.9                        52 CHO                       C.sub.6 H.sub.5                                                                         C.sub.6 H.sub.5                          53 CHO                       H        C(CH.sub.3).sub.3                        54 CHO                       H        (CH.sub.2).sub.9 CH.sub.3                55 CHC(CN).sub.2             H        CHC(CN).sub.2                            56 CHNNHCONH.sub.2           H        H                                        57 CHNNHCSNH.sub.2           H        H                                        58 CHC(CN)CONHCH.sub.3       H        H                                        59 CHC(CN)CONHC.sub.6 H.sub.5                                                                               CHN(CH.sub.3).sub.2                                 60                                                                               ##STR15##                "                                                 61 CHC(CN)COC.sub.6 H.sub.5  H        C.sub.2 H.sub.5                            62                                                                               ##STR16##                H        H                                          63                                                                              CHC(CN)SO.sub.2 CH.sub.3  C.sub.2 H.sub.5                                                                         C.sub.6 H.sub.5                            64                                                                               ##STR17##                CH.sub.3 C.sub.6 H.sub.5                          65                                                                                 ##STR18##                CH.sub.3 C.sub.6 H.sub.5                            66                                                                               ##STR19##                H        C.sub.6 H.sub.5                          __________________________________________________________________________

In the following Table 2, further compounds of the invention of formula ##STR20## are given which may be prepared in analogy with the procedure of the foregoing Examples 1 to 3.

                  TABLE 2                                                          ______________________________________                                         EX.                                                                            No.            B                                                               ______________________________________                                         67             --CH.sub.2 CH.sub.2 Cl                                          68             --nC.sub.3 H.sub.7                                              69             --CH(CH.sub.3).sub.2                                            70             --CH.sub.2 CH.sub.2 CH.sub.2 Cl                                 71             --CH.sub.2 CH.sub.2 CH.sub.2 Br                                 72             --CH.sub.2 CH═CH.sub.2                                      73             --CH.sub.2 CBr═CH.sub.2                                     74             --CH.sub.2 CH═CHCl                                          75             --CH.sub.2 CCH                                                  76             --CH.sub.2 CH.sub.2 COOC.sub.2 H.sub.5                          77             --CH(CH.sub.2 OH)CH.sub.2 Cl                                    78             --CH(CH.sub.2 OCOCH.sub.3)CH.sub.2 Cl                           79             --CH.sub.2 CN                                                   80             --CH.sub.2 C(CH.sub.3)═CH.sub.2                             81             --CH.sub.2 CH═CHCH.sub.3                                    82             --nC.sub.4 H.sub.9                                              83             --CH.sub.2 CH(CH.sub.3).sub.2                                   84             --CH.sub.2 CH.sub.2 --OCOC.sub.2 H.sub.5                        85             --CH.sub.2 CHBrCH.sub.3                                         86             --nC.sub.5 H.sub.11                                             87             --nC.sub.6 H.sub.13                                             88             --CH.sub.2 C.sub.6 H.sub.4 (4-Cl)                               89             --CH.sub.2 C.sub.6 H.sub.4 (4-NO.sub.2)                         90             --CH.sub.2 CHBrCOOCH.sub.3                                      91             --CH(CH.sub.3)CH.sub. 2 OCOCH.sub.3                             92             --CH(C.sub.2 H.sub.5)CH.sub.2 OH                                93             --C(CH.sub.3).sub.3                                             94             --CH.sub.2 CH.sub.2 CHBrCH.sub.3                                95             --CH.sub.2 CH.sub.2 CH.sub.2 CHBrCH.sub.3                       96             --CH.sub.2 CHBrCH.sub.2 OH                                      97             --CH.sub.2 CHBrCOOH                                             98             --CH.sub.2 CBrCl.sub.2                                          99             --CH.sub.2 CH.sub.2 --OCONHC.sub.2 H.sub.5                      100            --CH.sub.2 CH.sub.2 CH(CH.sub.3).sub.2                          101            --CH.sub.2 CH.sub.2 CH═CH.sub.2                             102            --CH.sub.2 CH.sub.2 OCOCH.sub.3                                 103            --CH.sub.2 CH.sub.2 COOH                                        104            --CH.sub.2 CH.sub.2 CH.sub.2 COOC.sub.2 H.sub.5                 105            --CH.sub.2 CH.sub.2 OCOOCH.sub.3                                106            --CH.sub.2 CH.sub.2 OC.sub.6 H.sub.5                            107            --CH(CH.sub.3)C.sub.2 H.sub.5                                   108            --CH.sub.2 CHOHC.sub.2 H.sub.5                                  109            --CH.sub.2 CH.sub.2 CH.sub.2 OCOCH.sub.3                        110            --(CH.sub.2).sub.9 CH.sub.3                                     111            --CH.sub.2 COOCH.sub.3                                          112            --CH.sub.2 C(CH.sub.3).sub.3                                    113            --CH.sub.2 COOCH.sub.2 C.sub.6 H.sub.5                          114             nC.sub.8 H.sub.17                                              115            --CH(COOC.sub.2 H.sub.5).sub. 2                                 116            --CH.sub.2 CONH.sub.2                                           117            --CH(CH.sub.3)CH.sub.2 CH.sub.2 CH.sub.3                        118            --CH(CH.sub.3)COOC.sub.2 H.sub.5                                119            --CH.sub.2 CH.sub.2 CH.sub.2 C.sub.6 H.sub.5                    120            --CH.sub.2 CONHC.sub.6 H.sub.5                                  ______________________________________                                     

What is claimed is:
 1. A compound of the formula, ##STR21## in which R₁ is -CHO, -CH═CR₄ R₅, -CN, -CH═NOH, -CH₂ OR₆, -CH═N-NHR₇, ##STR22## or -CH(OH)CN, R₂ is hydrogen; C₁₋₁₀ alkyl; c₂₋₃ alkyl substituted by hydroxy, cyano, chlorine, bromine, alkyl-C₁₋₂ carbonyl, alkoxy-C₁₋₄ carbonyloxy, alkylC₁₋₄ carbonyloxy, alkylaminocarbonyloxy, dialkylaminocarbonyloxy, alkoxyC₁₋₄ carbonyl, phenylaminocarbonyloxy or N-alkyl-N-phenylaminocarbonyloxy with the proviso that such substituted alkyl radicals are free from acetal groups; phenyl optionally substituted by 1 or 2 substituents selected from chlorine, bromine, methyl and nitro; alkenyl; dicyanoalkenyl; cyclohexyl; or naphthyl,and R₃ has one of the significances of R₂ with the proviso that when one of R₂ and R₃ is naphthyl the other has a significance other than naphthyl or phenyl, and when one of R₂ and R₃ is dicyanoalkenyl the other is hydrogen, or, R₂ and R₃ together with the nitrogen atom form a piperidine, piperazine or morpholine ring, or R₂ and R₃ together form a group of formula

    ═CH-(CH═CH).sub.m' NR.sub.10 R.sub.11

in which either, R₁₀ is hydrogen or alkyl, and R₁₁ is hydrogen, alkyl or phenyl, or, R₁₀ and R₁₁ together with the N-atom form piperidine, with the proviso that R₂ and R₃ are both hydrogen when R₁ is other than --CHO or --CH═CR₄ R₅ and at least one of R₂ and R₃ is other than hydrogen when R₁ is --CH═CR₄ R₅, either R₄ is hydrogen, cyano, alkylcarbonyl benzoyl, alkylsulphonyl, phenylsulphonyl, alkylaminocarbonyl, dialkylaminocarbonyl, phenylaminocarbonyl, N-alkyl-N-phenylaminocarbonyl, aminocarbonyl, aminocarbonylaminocarbonyl, piperidinylcarbonyl, aminothiocarbonyl, benzimidazolyl-2 or -COOB, in which B is hydrogen; C₁₋₁₀ alkyl; C₅₋₇ cycloalkyl; C₁₋₆ alkyl substituted by up to three substituents selected from the group consisting of chlorine and bromine; C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxyl, cyano, phenoxy, alkoxy, carboxy, alkoxycarbonyloxy, alkylcarbonyloxy, alkoxycarbonyloxy, alkylaminocarbonyloxy, aminocarbonyl, alkylaminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, and phenyl, in which the phenyl ring is optionally substituted by 1 or 2 substituents selected from chlorine, bromine and nitro, with the proviso that when such alkyl is substituted by a group containing a benzene ring it is monosubstituted and any substituted alkyl is free from acetal groups or B is C₃₋₆ alkenyl optionally substituted by chlorine or bromine; or is alkynyl, and R₅ is hydrogen, cyano, alkoxycarbonyl, nitro or 3-di-cyanomethylene-5-5-dimethylcyclohene-1-yl with the proviso that when R₅ is the latter R₄ is hydrogen and when R₅ is nitro R₄ is hydrogen, methyl or ethyl, or R₄ and R₅ together form a ring system of the formula ##STR23## R₆ is hydrogen, alkyl, alkylcarbonyl or benzyl in which the benzene ring is optionally substituted by up to two substituents selected from chlorine, bromine and nitro, R₇ is hydrogen, alkyl, aminocarbonyl, amino thiocarbonyl or phenyl which is optionally substituted by 1 or 2 substituents selected from the group consisting of chlorine, bromine and nitro, R₈ is hydrogen, chlorine, bromine, methyl, C₁₋₂ alkoxy, carboxyl, alkoxycarbonyl, cyano or nitro, m is 0 or 1, m' is 0 or 1,and any alkyl and alkoxy groups or moieties in such compounds contain 1 to 4 carbon atoms and any alkenyl or alkynyl groups or moieties 3 to 4 carbon atoms, except when otherwise stated.
 2. A compound according to claim 1in which R₂ is hydrogen; C₁₋₁₀ alkyl; C₂₋₃ alkyl substituted by hydroxy, cyano, chlorine, bromine, alkyl-C₁₋₂ carbonyl, alkoxy-C₁₋₄ carbonyloxy, alkyl-C₁₋₄ carbonyloxy, alkylaminocarbonyloxy, dialkylaminocarbonyloxy, alkoxy-C₁∝4 carbonyl, phenylaminocarbonyloxy or N-alkyl-N-phenylaminocarbonyloxy with the proviso that such substituted alkyl radicals are free from acetal groups; phenyl optionally substituted by 1 or 2 substituents selected from chlorine, bromine, methyl and nitro; alkenyl; dicyanoalkenyl; cyclohexyl; or naphthyl, and R₃ has one of the significances of R₂ with the proviso that when one of R₂ and R₃ is naphthyl the other has a significance other than naphthyl or phenyl, and when one of R₂ and R₃ is dicyanoalkenyl the other is hydrogen, or R₂ and R₃ together form a group of formula

    ═CH--(CH═CH).sub.m' NR.sub.10 R.sub.11

R₄ is hydrogen, cyano, alkylcarbonyl, benzoyl, alkylsulphonyl, phenylsulphonyl, alkylaminocarbonyl, dialkylaminocarbonyl, phenylaminocarbonyl, N-alkyl-N-phenylaminocarbonyl, aminocarbonyl, aminocarbonylaminocarbonyl, aminothiocarbonyl, or --COOB, in which B is hydrogen; C₁₋₁₀ alkyl; C₅₋₇ cycloalkyl; C₁₋₆ alkyl substituted by up to three substituents selected from the group consisting of chloride and bromine; C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxyl, cyano, phenoxy, alkoxy, carboxy, alkoxycarbonyl, alkylcarbonyloxy, alkoxycarbonyloxy, alkylaminocarbonyloxy, aminocarbonyl, alkylaminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, and phenyl, in which the phenyl ring is optionally substituted by 1 or 2 substituents selected from chlorine, bromine and nitro, with the proviso that when such alkyl is substituted by a group containing a benzene ring, it is monosubstituted and any substituted alkyl is free from acetal groups; or B is C₃₋₆ alkenyl optionally substituted by chlorine or bromine; or is alkynyl, and R₅ is hydrogen, cyano, alkoxycarbonyl, nitro or 3-di-cyanomethylene-5-5-dimethylcyclohexen-1-yl with the provisos that when R₅ is the latter R₄ is hydrogen and when R₅ is nitro R₄ is hydrogen, methyl or ethyl, R₁₀ is hydrogen or alkyl, and R₁₁ is hydrogen, alkyl or phenyl.
 3. A compound according to claim 2 whereinR₁ is R₁ ', where R₁ ' is --CHO, --CH═CR₄ R₅, --CH═NOH or CN, R₂ is R₂ ', where R₂ ' is hydrogen, C₁₋₄ alkyl, hydroxyethyl, cyanoethyl or phenyl, R₃ is R₃ ', where R₃ ' is hydrogen, C₁₋₄ alkyl, allyl, cyclohexyl, or naphthyl, or R₂ ' and R₃ ' form a group of formula ═CH(CH═CH)_(m) 'NR₁₀ R₁₁, where R₁₀ and R₁₁ are C₁₋₄ alkyl, R₄ is R₄ ', where R₄ ' is cyano; benzoyl; methylsulphonyl; phenylsulphonyl; methyl or ethylaminocarbonyl; phenylaminocarbonyl; aminocarbonyl; aminocarbonylaminocarbonyl; or --COOB', where B' is C₁₋₁₀ alkyl, cyclohexyl, C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxy, cyano, C₁₋₂ alkoxy, carboxy, alkoxy(C₁₋₂)carbonyl, alkyl(C₁₋₂)carbonyloxy, C₁₋₂ alkoxycarbonyloxy, C₁₋₂ alkylaminocarbonyloxy, aminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, phenyl, chlorophenyl, nitrophenyl, with the proviso that when such alkyl is substituted by a group containing a benzene ring, it is monosubstituted and any substituted alkyl is free from acetal groups or B' is alkenyl optionally substituted by chlorine or bromine or is alkynyl, and R₅ is R₅ ', where R₅ ' is cyano, nitro or 3-dicyanomethylene-5,5-dimethylcyclohexen-1-yl with the proviso that when R₅ ' is any one of the latter two significances, R₄ is hydrogen.
 4. A compound according to claim 1, in which m and m' are both
 0. 5. A compound according to claim 1, in which any C₁₋₄ alkyl group or moiety in R₄ contains 1 or 2 carbon atoms.
 6. A compound according to claim 4, in which R₂ is R₂ ', where R₂ ' is hydrogen, C₁₋₄ alkyl, hydroxyethyl, cyanoethyl or phenyl and R₃ is R₃ ', where R₃ ' is hydrogen, C₁₋₄ alkyl, allyl, cyclohexyl, naphthyl or phenyl, or R₂ ' and R₃ ' together form a group of formula ═CHNR₁₀ R₁₁, where R₁₀ and R₁₁ are C₁₋₄ alkyl.
 7. A compound according to claim 6, in which when R₃ ' is cyclohexyl or phenyl, R₂ ' is other than phenyl and when R₃ ' is naphthyl R₂ ' is hydrogen.
 8. A compound according to claim 4, in which R₁ is R₁ ', where R₁ ' is --CHO, --CH═CR₄ R₅, --CH═NOH or CN.
 9. A compound according to claim 7, in which R₁ is --CHO or --CH═CR₄ R₅.
 10. A compound according to claim 9, in which R₄ is R₄ ', where R₄ ' is cyano; benzoyl; methylsulphonyl; phenylsulphonyl; methyl or ethylaminocarbonyl; phenylaminocarbonyl; aminocarbonyl; aminocarbonylaminocarbonyl; piperidinylcarbonyl; benzimidazolyl-2 or --COOB', where B' is C₁₋₁₀ alkyl, cyclohexyl, C₁₋₆ alkyl substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxy, cyano, C₁₋₂ alkoxy, carboxy, alkoxy(C₁₋₂)carbonyl, alkyl(C₁₋₂)carbonyloxy, C₁₋₂ alkoxycarbonyloxy, C₁₋₂ alkylaminocarbonyloxy, aminocarbonyl, phenylaminocarbonyl, benzyloxycarbonyl, phenyl, chlorophenyl, nitrophenyl, with the proviso that when such alkyl is substituted by a group containing a benzene ring it is monosubstituted and any substituted alkyl is free from acetal groups; or B' is alkenyl optionally substituted by chlorine or bromine or is alkynyl. and R₅ is R₅ ', where R₅ ' is cyano, nitro or β-(3-dicyanomethylene-5,5-dimethylcyclohexen-1-yl)vinyl with the proviso that when R₅ ' is any one of the latter two significances R₄ is hydrogen.
 11. A compound according to claim 9, in which R₁ is R₁ "', where R₁ "' is --CHO or --CH═C(CN)R₄ ", where R₄ " is cyano, alkoxy(C₁₋₆)carbonyl, benzoyl, cyclohexyloxycarbonyl, C₃₋₄ -alkenyloxycarbonyl, chloro- or bromoC₃₋₄ alkenyloxycarbonyl or alkoxy(C₁₋₆)carbonyl in which the alkyl group is substituted by up to two substituents selected from the group consisting of chlorine, bromine, hydroxyl phenyl, carboxy, alkoxyC₁₋₂ carbonyl, alkyl(C₁₋₂)carbonyloxy, C₁₋₂ alkylaminocarbonyloxy, alkoxyC₁₋₂ carbonyloxy.
 12. A compound according to claim 11, in which R₂ ' and R₃ ' are both hydrogen or R₂ ' and R₃ ' together form ═CH--N(CH₃)₂.
 13. A compound according to claim 1, in which m is
 0. 14. A compound according to claim 12 of formula ##STR24##
 15. A compound according to claim 12 of formula ##STR25##
 16. A compound according to claim 1, in which R₂ and R₃ have a significance other than together forming a heterocyclic ring and R₄ and R₅ have a significance other than forming a carbocyclic or heterocyclic ring system.
 17. A compound according to claim 16, in which m and m' are
 0. 18. A compound according to claim 1 of the formula ##STR26## in which one of R₂ and R₃ is other than hydrogen.
 19. A compound according to claim 1wherein R₁ is --CHO, --CH═CR₄ R₅, --CH--NOH, --CH₂ OR₆, --CH═N--NHR₇, ##STR27## or --CH(OH)CN.
 20. A compound according to claim 4,wherein R₁ is --CHO, --CH═CR₄ R₅, --CH--NOH, --CH₂ OR₆, --CH═N--NHR₇, ##STR28## or --CH(OH)CN.
 21. A compound according to claim 6,in which R₁ is --CHO, --CH═CR₄ R₅, --CH--NOH, --CH₂ OR₆, --CH═N--NHR₇, ##STR29## or --CH(OH)CN.
 22. A compound according to claim 6,in which R₁ is --CHO or --CH═CR₄ R₅.
 23. A compound according to claim 16,wherein R₁ is --CHO, --CH═CR₄ R₅, --CH--NOH, --CH₂ OR₆, --CH═N--NHR₇, ##STR30## or --CH(OH)CN.
 24. A compound according to claim 16,wherein R₁ is --CHO or --CH═CR₄ R₅.
 25. A compound according to claim 2,wherein R₁ is --CHO, --CH═CR₄ R₅, --CH--NOH, --CH₂ OR₆, --CH═N--NHR₇, ##STR31## or --CH(OH)CN.
 26. A compound according to claim 2,wherein R₁ is --CHO or --CH═CR₄ R₅.
 27. A compound according to claim 3,wherein R₁ is --CHO or --CH═CR₄ R₅.
 28. A process for the production of a compound, as defined in claim 1 and in which R₁ is formyl, comprising reacting a compound of formula ##STR32## or a salt thereof, with a Vilsmeier complex comprising a formamide and an acid chloride, and optionally hydrolytically converting an imino group as R to a primary amine.
 29. A process according to claim 28, in which the Vilsmeier complex comprises phosphorousoxychloride and dimethylformamide. 